Our goals for the second year of the project will be concerned with purification of the 100,000 dalton remnant with ristocetin co-factor activity, study of its subunit polypeptide chain components, immunologic structure, amino terminal ends and total amino acid content. We will also be concerned with tryptic degradation of the parent von Willebrand protein and the 100,000 dalton remnant to the smallest components possible with this enzyme, in order to study possible minimum repeating anatomic units of this highly polymerized molecule. Ultracentrifugal studies will continue with the objective of finding a directly measured molecular size for both the parent Willebrand protein species and for the degradative remnants obtained by enzymes or disulfide bond reduction.